The following summary describes five projects that attempt to investigate, at the molecular level, the roles a number of molecules, including, A kinase, kinesin light chains, the modulatory neuropeptides buccalin and myomodulin, rab 3 and a novel protein thought to regulate a cdc~2~like protein found exclusively in neurons, play in neural function. We have characterized the peptide families of buccalin and myomodulin from the sea hare Aplysia californica in an attempt to gain further insights as to how peptide families collectively contribute to pre~ or postsynaptic neuromodulation. The molecular characterization of peptide receptors through which signal transduction cascades are activated to affect modulation, for example G protein~coupled receptors, and their respective regulation by A kinases is also being actively pursued. A family of kinesin light chain transcripts have been identified in the nervous system of the squid Loligo pealei. Protein over~expression and purification is currently being employed as a means to determine function and specificity as they relate to intracellular transport, particularly axonal transport of membrane bound organelles in neurons. The small, synaptic vesicle~specific, GTP~binding protein, rab 3a, has been cloned from the squid optic lobe. Microinjection experiments utilizing either whole protein or fragments of over~expressed rab 3a, and rab 3a peptide~specific antibodies will be used to help determine the role rab 3a plays in synaptic vesicle docking and or fusion at the presynaptic membrane. A fifth protein, p62, thought to regulate the activity of a neurofilament~specific cdc~2 protein kinase~like activity has been cloned and characterized from a rat brain cDNA library.